1. Field of the Invention
The present invention relates to a molding machine for producing plastic hollow bodies and including at least one extrusion die for producing a preform, injection plunger means for delivering plasticized plastic material to the at least one extrusion die, a triggering device displaceable toward and away from the at least one extrusion die, two blow mold halves arranged between the extrusion die and the triggering device and displaceable toward each other for forming a blow mold in which the preform produced by the extrusion die is received and a hollow body is formed upon gas being blown in by the triggering device, a computerized control means, a weight-measuring device for determining weight of the hollow bodies and further control means.
2. Description of the Prior Art
A molding machine of the above-described type, but without a weight-measuring device and other measuring means is disclosed in European patent No. 535,254. Generally, it is known to provide a molding machine, which is disclosed in this European Patent, with a weight-measuring device. The control of produced hollow bodies is effected in a following manner. A hollow body is cut up, according to its length, in three sections, and the thickness is measured at the edges of the cuts. Also, transitional regions at sharp bends of the hollow body profile or at the cuts as well as the end regions of the hollow body and adjoining them middle regions are examined. However, one cannot exclude a possibility of an error during a mass production of hollow bodies, which leads to undesired deviations of the wall thickness. A wall thickness error leads to a premature breaking of a hollow body when it is subjected to a certain stress. A wall thickness error also results in too thick or too thin regions in a hollow body or in formation of a hole in the hollow body. At present, the control of the quality of hollow body is effected manually, which is expensive. The cuts made in a hollow body make it defective and results in a loss of the hollow body. Because not all of the formed hollow bodies are subjected to cut-up, the testing of the non cut-up hollow bodies is incomplete. However, in many cases, e.g., in manufacturing of motor vehicles it is desired that each separate hollow body be subjected to a precise control.
Accordingly, an object of the present invention is to provide a molding machine of the type described above in which each hollow body is automatically tested as to whether it has a uniform wall thickness.